This invention relates generally to fuel injector performance variability and control signal adjustments to reduce the same, and more particularly to an in-chassis determination of fuel injector, timing delay and quantity deviations, and control signal adjustments, based on the same.
It is known in the art that fuel injector performance can vary as a function of at least one of on-time, temperature and rail pressure. Fuel injector performance includes a timing delay and quantity of fuel injected. Timing delay relates to the delay from the start of control signal to a start of injection. This aspect of variance from nominal injector performance is a result of factors such as the machining tolerances of fuel injector components. In addition, these fuel injector performance deviations can change over the life of the fuel injector.
For instance, fuel injectors typically exhibit changes in their performance characteristics after an initial period of use. In particular, fuel injectors tend to experience an increase in the amount of fuel injected over a range of operating conditions after this breaking-in period. While this change in injection characteristics does not render the fuel injectors, or the engine into which they are incorporated, unfit for use, it can contribute to performance inconsistencies. For example, in engines utilizing smoke limiting maps, fuel injector limiting maps are used to limit the amount of fuel injected by fuel injectors during certain operating conditions to reduce undesirable engine emissions. However, when the fuel injectors are not performing in a manner that is consistent with the stored fuel injector performance curves, the effectiveness of these smoke limiting maps can be compromised.
Evaluation of fuel injector performance has been previously addressed in the art. For instance, one known method of evaluating fuel injector performance involves removing an engine from a vehicle and connecting it to a dynamometer. The engine is then operated for a number of cycles, with the performance of the fuel injectors being monitored while the dynamometer absorbs the engine load. While this fuel injector evaluation method has proven effective, it can be expensive and unrealistic for engine owners. In addition, because the engine must be removed from the vehicle, the test must be performed by trained personnel, typically at a service center. Thus, ascertaining injector performance characteristics at any given time is problematic.
Another such method is taught by Thomas in U.S. Pat. No. 5,839,420, entitled System and Method of Compensating for Injector Variability, and issued on Nov. 24, 1998. This method or system determines an appropriate calibration code for each injector based on a quantity performance difference of the injector compared to a nominal fuel injector. A logic controller uses this calibration code to alter on-times determined by the engine control unit, thus causing the injector to inject quantities more like a nominal injector, and cause a group of injectors to perform more uniformly. However, correcting for quantity deviations is only part of a total strategy; Thomas fails to address how to quantify and correct for timing delay variability among a group of injectors installed in an engine.
The present invention is directed to overcoming one or more of the problems as set forth above.
In in-chassis fuel injector diagnostic system includes a plurality of electronically controlled fuel injectors attached to an engine that is mounted on a chassis. At least one electromotive sensor is operably coupled to at least one of the electronically controlled fuel injectors. An electronic control module is in communication with the electronically controlled fuel injectors and the electromotive sensor. The electronic control module includes a fuel injector quantity deviation algorithm and a fuel injector timing deviation algorithm.
In another aspect, a method of determining a fuel injector performance deviation from nominal includes a step of estimating a fuel injection quantity deviation. This is accomplished at least in part by operating an engine with less than all cylinders in a power mode, and determining at least one of an injector response and an engine response. The method also includes a step of estimating a fuel injection timing deviation. This is accomplished at least in part by coupling an electromotive sensor with an electronically controlled valve of a fuel injector, and energizing the electronically controlled valve.
In still another aspect, a method of in-chassis trimming of fuel injector operation in an engine includes a step of performing timing deviation in-chassis diagnostic testing. The timing deviation data is stored in memory. Quantity deviation in-chassis diagnostic testing is also performed, and the deviation data is also stored in memory. A control signal to a fuel injector is adjusted based at least in part on the quantity deviation data and timing deviation data.